Create interest is a 'saved search'. When you browse coffees you can save your search by 'creating an interest'. If there's no coffees available that match your search, you can 'create an interest' so you will be notified when a coffee that matches your search will become available. On another hand it is useful to 'create an interest' if you want to come back to the overview of coffees you searched for on a later moment. Your created interests will be summarised under 'My interests' in your personal drop down menu on the right top corner.